CN116322107A

CN116322107A - Laminated organic electroluminescent device

Info

Publication number: CN116322107A
Application number: CN202310072658.2A
Authority: CN
Inventors: 王志恒; 陈启燊; 梁洁; 宋小贤; 毕海; 王悦
Original assignee: Ji Hua Laboratory
Current assignee: Ji Hua Laboratory
Priority date: 2023-01-31
Filing date: 2023-01-31
Publication date: 2023-06-23

Abstract

The invention relates to the technical field of organic photoelectric materials and devices, in particular to an organic electroluminescent device, which comprises an anode layer, a hole transmission layer, at least two light-emitting layers, an electron transmission layer, a cathode layer and a connecting layer, wherein the anode layer, the hole transmission layer, the at least two light-emitting layers, the electron transmission layer and the cathode layer are sequentially arranged from bottom to top; the connecting layer comprises a first connecting layer and a second connecting layer, the first connecting layer and the second connecting layer are respectively connected with the two adjacent light-emitting units, and the first connecting layer is formed into an alternate lamination structure by m sub-electron transmission units and n ultrathin layers. According to the invention, a multi-carrier separation channel can be formed by introducing a multi-layer alternating structure into the connecting layer of the laminated OLED device, the carrier generating capacity of the connecting layer is improved, and electrons are promoted to be injected into the electron transmission layer of the light-emitting unit, so that the voltage drop of the connecting layer is reduced, the rising trend of the driving voltage in the aging process of the device is restrained, and the laminated OLED device with low driving voltage, high efficiency and long service life is realized.

Description

Laminated organic electroluminescent device

Technical Field

The invention relates to the technical field of organic photoelectric materials and devices, in particular to an organic electroluminescent device.

Background

An Organic Light-emitting Diode (OLED) technology is a technology of emitting Light under the action of an applied voltage, and has many advantages of flexibility, self-luminescence, lightness, thinness, low power consumption and the like, and has been widely applied to the fields of smart phones, wearable devices, vehicle-mounted displays and the like. The organic electroluminescent device structure and the preparation process thereof play a crucial role in representing the luminous performance of the OLED material, and are one of the key parts of OLED display and illumination technology. Therefore, the exploration of a new OLED device structure with low driving voltage, high luminous efficiency and long service life and the preparation process thereof become a research hot spot in the current OLED technical field.

Among the numerous OLED lighting products, OLED automotive lighting is one of the key application panels. Compared with LED automobile illumination, the OLED automobile illumination product has the advantages of uniformity in light emission, portability, ultra-thin light emission, partition matrixing and the like. In recent years, OLED automotive lighting products have gradually penetrated into the fields of automotive interior lighting, automotive taillights (daytime running lights), instrument panel indicator lights and the like, and for example, bma M4, audi A8, red flag H9 and the like have successively adopted deep red OLED lighting panels as automotive taillight light sources, and it is believed that OLED automotive lighting applications will be further expanded in the future. Automotive lighting, particularly taillight lighting, places more stringent requirements in terms of drive voltage, light emission brightness, operating temperature, and device lifetime than traditional OLED lighting applications. For this purpose, a stacked OLED device is typically obtained by combining a plurality of light emitting cells in series using a connection layer (Charge generation layer, CGL) structure. A light emitting cell typically comprises at least one light emitting layer, a hole transporting layer and an electron transporting layer. Compared with a single-light-emitting layer OLED device, the light-emitting brightness and the service life of the stacked device under the driving of the same current density are improved by times. That is, at the same brightness, the current density required for the stacked OLED is smaller than that of the conventional single-layer OLED, thereby achieving the effect of extending the lifetime; however, at constant current density the luminance of the stacked OLED is higher than that of a conventional single-layer OLED, and the voltage increases. Therefore, for stacked OLED devices, reducing the driving voltage drop of the connection layer between the light emitting units is critical to achieving high performance stacked OLED devices. On the other hand, when the OLED device is aged with constant current driving, there is generally a decrease in the luminance of the device and an increase in the driving voltage, because a luminescence quenching center, a carrier capturing center, and a non-radiative transition center are generated during the aging of the device, resulting in annihilation of excitons of a radiative transition and a decrease in luminance, and electrons or holes for transport are captured by the carrier capturing center of a deep energy level, resulting in an increase in the driving voltage. Slowing down the decay of device brightness and the trend of driving voltage rise will promote the operating life of OLED device, especially for constant voltage driven illumination panel, and it is important to restrain the driving voltage rise in the device ageing process, is the key of obtaining long-life OLED device.

In terms of improving the performance of the connection layer, researchers and panel manufacturers have performed systematic optimization work, for example, in patent application CN114520301a, a stacked organic light emitting device is disclosed, a spacer layer structure is introduced between an n-type doped layer and a p-type doped layer, so that n-type dopants are prevented from easily diffusing into the p-type doped layer and an adjacent light emitting layer, and thus the driving voltage of the device is increased, and on the other hand, the injection and balance of carriers are improved by optimizing the collocation of a charge generating layer and an adjacent compound, so that the overall performance of the device is improved; for another example, in the patent application KR20170062938, the voltage is reduced, the efficiency is improved, and the lifetime is improved by optimizing the matching of the p-type charge generation layer and the hole transport layer in contact with the p-type charge generation layer in terms of energy level and hole mobility.

However, in the prior art, the research on the relation between the connection layer structure of the stacked device and the aging effect of the device is less, and the contribution and the internal mechanism of the aging of the connection layer to the brightness attenuation and the driving voltage rise of the device cannot be further clarified, so that a connection layer structure scheme for inhibiting the brightness drop and the voltage rise in the aging process of the device and improving the stability of the OLED device is required to be obtained.

Disclosure of Invention

In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a new connection layer structure scheme for a stacked OLED device, by disposing an ultrathin layer containing an n-type dopant material in a first connection layer in the connection layer, a multilayer alternate combination structure of ultrathin layers and sub-electron transport units is formed, and the electron transport layers of the alternate combination structure can effectively improve carrier separation and electron injection capabilities of the connection layer, inhibit voltage rise during device aging, improve life stability of the device, and prepare a stacked OLED device with low driving voltage, high efficiency and long lifetime.

The invention provides a laminated organic electroluminescent device, which comprises an anode layer, at least two light-emitting units, a cathode layer and a connecting layer, wherein the anode layer, the at least two light-emitting units and the cathode layer are sequentially arranged from bottom to top; the connecting layer comprises a first connecting layer and a second connecting layer, the first connecting layer and the second connecting layer are respectively connected with the two adjacent light-emitting units, and the first connecting layer is formed by alternately laminating m sub-electron transmission units and n ultrathin layers.

Further, the ultra-thin layer comprises an n-type dopant material, preferably at least one from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, gold, silver, copper, iron, nickel, platinum, palladium, ruthenium, ytterbium, molybdenum trioxide, vanadium pentoxide, tungsten trioxide, cesium fluoride, cesium carbonate, lithium fluoride, lithium carbonate, lithium 8-hydroxyquinolinate, sodium chloride, ferric chloride, and ferric oxide.

Further, the m and n are integers between 2 and 10.

Further, the sub-electron transport unit is composed of a first organic material selected from at least one of the following compounds (1-1) to (1-21):

further, the sub-electron transport unit is composed of an n-type dopant material and a second organic material;

the n-type dopant material is selected from one of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, gold, silver, copper, iron, nickel, platinum, palladium, ruthenium, ytterbium, molybdenum trioxide, vanadium pentoxide, tungsten trioxide, cesium carbonate, lithium carbonate, sodium chloride, ferric chloride and ferric oxide;

the second organic material is selected from at least one of the compounds (5-1) to (5-42):

further, the second connection layer comprises one or two of a P-type dopant and an aromatic amine compound.

Further, the P-type dopant of the second connection layer is at least one of MoO3, WO3, V2O5, moO2, co3O4, and the following compounds (HI-1) to (HI-20);

further, the mass percentage of the n-type dopant material of the sub electron transport unit is 0.1-50wt%;

further, the thickness of the ultrathin layer is 0.1-5nm, and the thickness of the sub electron transport unit is 3-30 nm;

an apparatus for laminating organic electroluminescent devices, the apparatus including the above-described organic electroluminescent device, and not being limited to the organic electroluminescent device, includes a display device, a lighting device, a solar cell, a lighting element, an organic thin film transistor, an organic field effect transistor, an organic thin film solar cell, an information tag, or an electronic paper, which are made using the above-described device structure and material.

Compared with the prior art, the invention has the beneficial effects that:

(1) Introducing an ultrathin layer containing n-type dopant and a sub-electron transport unit into a first connecting layer of a connecting layer of the laminated OLED device to form an alternating laminated structure, wherein the alternating laminated structure can form a multi-carrier separation channel, so that the carrier generating capacity of the connecting layer is improved, electrons are promoted to be injected into the electron transport layer of the light-emitting unit, the voltage drop of the connecting layer is reduced, and the laminated OLED device with low driving voltage and high efficiency is realized;

(2) The multilayer alternating structure comprising the n-type dopant ultrathin layer and the sub-electron transport unit can prevent alkali metal of the connecting layer from migrating from the connecting layer into the light-emitting layer, so that light-emitting excitons are quenched by the metal, and the service life of the device is prolonged; further, the ultrathin layer can inhibit ageing action and decomposition of the material of the electron transport layer, and relieve voltage rise caused by ageing of the material, so that the driving voltage rise trend in the ageing process of the device is inhibited, and the long-life OLED device performance is obtained.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the following description will briefly explain the drawings used in the embodiments or the description of the prior art, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 shows a schematic structure of a stacked organic electroluminescent device of the present invention;

fig. 2 shows a device lifetime characteristic diagram of example 1 and comparative example 1 of the present invention;

fig. 3 shows graphs of driving voltage changes during device aging of example 1 and comparative example 1 of the present invention.

In the figure: 100. an anode layer; 101. a hole injection layer; 102. a first hole transport layer; 103. a second hole transport layer; 104. a first light emitting layer; 105. a second electron transport layer; 106. a first electron transport layer; 107. a first connection layer; 107-1, a first ultrathin layer; 107-2, a first sub-electron transport unit; 107-3, a second ultrathin layer; 107-4, a second sub-electron transport unit; 107-n, nth ultrathin layer; 107-m, m-th sub-electron transport unit; 108. a second connection layer; 109. a first hole transport layer; 110. a second hole transport layer; 111. a second light emitting layer; 112. a second electron transport layer; 113. a first electron transport layer; 114. an electron injection layer; 115. and a cathode layer.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present disclosure more apparent, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present disclosure. It will be apparent that the described embodiments are some, but not all, of the embodiments of the present disclosure. All other embodiments, which can be made by one of ordinary skill in the art without the benefit of the present disclosure, are intended to be within the scope of the present invention based on the described embodiments.

It is to be understood that any and all embodiments of the invention may be combined with any other embodiment or features of multiple other embodiments to yield yet further embodiments without conflict. The present invention includes such combinations resulting in additional embodiments. In this specification, groups and substituents thereof can be selected by one skilled in the art to provide stable moieties and compounds. When substituents are described by conventional formulas written from left to right, the substituents also include chemically equivalent substituents obtained when writing formulas from right to left.

The section headings used in this specification are for organizational purposes only and are not to be construed as limiting the subject matter described. All documents or portions of documents cited in this disclosure, including but not limited to patents, patent applications, articles, books, operating manuals, and treatises, are hereby incorporated by reference in their entirety.

Unless otherwise specified, all technical and scientific terms used herein have the standard meaning of the art to which the claimed subject matter belongs. In case there are multiple definitions for a term, the definitions herein control.

As used herein, the singular forms "a", "an", and "the" are understood to include plural referents unless the context clearly dictates otherwise. Furthermore, the term "comprising" is an open-ended limitation and does not exclude other aspects, i.e. it includes the content indicated by the invention.

As shown in fig. 1, the present invention provides a stacked organic electroluminescent device, which is composed of an anode layer, at least two light emitting units, a cathode layer, and a connection layer for connecting two adjacent light emitting units, wherein the light emitting units are sequentially provided with a hole injection layer, a hole transport layer, a light emitting layer, and an electron transport layer from a side close to the anode layer.

Next, a light emitting unit of the laminated organic electroluminescent device of the present application will be further described. Further, the hole transport layer of the organic electroluminescent device, which is an organic layer formed between the light emitting layer and the anode layer (or hole injection layer), mainly serves to transport holes from the anode to the light emitting layer. The hole transport layer may be composed of a layer of organic layer material, defined as a first hole transport layer; it is also possible to consist of two layers of organic layer material, the organic layer on the side close to the anode layer being defined as a first hole transport layer and the organic layer on the side close to the light-emitting layer being defined as a second hole transport layer. As the hole transporting material for the hole transporting layer, an aromatic amine compound is preferably used, wherein the aromatic amine compound is at least one of a first aromatic amine derivative having a structural formula (i) and a second aromatic amine derivative having a structural formula (ii),

wherein Ar1 to Ar4 represent a substituted or unsubstituted aromatic hydrocarbon group having 6 to 50 (preferably 6 to 30, more preferably 6 to 20, still more preferably 6 to 12) ring-forming carbon atoms, a substituted or unsubstituted condensed aromatic hydrocarbon group having 6 to 50 (preferably 6 to 30, more preferably 6 to 20, still more preferably 6 to 12) ring-forming carbon atoms, a substituted or unsubstituted aromatic heterocyclic group having 5 to 50 (preferably 5 to 30, more preferably 5 to 20, still more preferably 5 to 12) ring-forming carbon atoms, or a substituted or unsubstituted condensed aromatic heterocyclic group having 5 to 50 (preferably 5 to 30, more preferably 5 to 20, still more preferably 5 to 12) ring-forming carbon atoms, or a group in which these aromatic hydrocarbon groups or condensed aromatic hydrocarbon groups are bonded to an aromatic heterocyclic group or a condensed aromatic heterocyclic group. Rings may be formed between Ar1 and Ar2, and between Ar3 and Ar 4.

L represents a substituted or unsubstituted aromatic hydrocarbon group having 6 to 50 (preferably 6 to 30, more preferably 6 to 20, still more preferably 6 to 12) ring-forming carbon atoms, or a substituted or unsubstituted condensed aromatic hydrocarbon group having 6 to 50 (preferably 6 to 30, more preferably 6 to 20, still more preferably 6 to 12) ring-forming carbon atoms, or a substituted or unsubstituted aromatic heterocyclic group having 5 to 50 (preferably 5 to 30, more preferably 5 to 20, still more preferably 5 to 12) ring-forming carbon atoms, or a substituted or unsubstituted condensed aromatic heterocyclic group having 5 to 50 (preferably 5 to 30, more preferably 5 to 20, still more preferably 5 to 12) ring-forming carbon atoms.

Further, the hole transport layer of the organic electroluminescent device of the present invention, the compound according to the structural formula (i) and the structural formula (ii) is preferably selected from the following compounds, but is not limited to the following structures:

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the hole injection layer is mainly used to promote injection of holes from the anode layer to the hole transport layer or the light-emitting layer, thereby realizing reduction of driving voltage of the organic electroluminescent device and improvement of light-emitting luminance and device life.

Wherein, the structural formulas of HI-1 to HI-20 are shown as follows:

further, the film thickness of the hole injection layer is not particularly limited, and is preferably 5 to 100nm.

Further, the film thickness of the hole transport layer is not particularly limited, and is preferably 20 to 200nm. Wherein when the hole transport layer of the organic electroluminescent device is composed of the first hole transport layer, the film thickness of the first hole transport layer is preferably 20 to 200nm; when the hole transport layer of the organic electroluminescent device is composed of a first hole transport layer and a second hole transport layer, the film thickness of the first hole transport layer is preferably 19 to 150nm, and the film thickness of the second hole transport layer is preferably 1 to 50nm.

Specifically, when the hole transport layer contains the p-type dopant and the hole transport material, the doping concentration of the p-type dopant is preferably 0.1 to 20.0wt%.

Further, the light emitting layer of the organic electroluminescent device has a main function of recombining holes and electrons injected into the light emitting layer to generate excitons, and the excitons complete an electro-optic conversion process by a radiation transition mode. The material constituting the light-emitting layer may be an undoped light-emitting compound composed of only the first compound, may be a binary light-emitting composition composed of the first compound and the third compound, or may be a ternary light-emitting composition composed of the first compound, the second compound, and the third compound.

Specifically, as the first compound, a fluorescent material, a phosphorescent material, a thermally activated delayed fluorescent material, or the like, which is selected according to a light emission mechanism, is preferable, and a phosphorescent material containing a coordinated metal such as iridium, platinum, or the like, a thermally activated delayed fluorescent material containing a boron nitrogen derivative, a boron oxygen derivative, an indolocarbazole derivative, or a boron fluorine derivative, and a fluorescent material containing a fluoranthene derivative, a pyrene derivative, or an imidazole derivative are selected as the first compound. The second compound preferably contains a benzonitrile derivative, a triazine derivative, a pyrimidine derivative, a pyridine derivative, a pyrazine derivative, an imidazole derivative, a derivative of benzothiophene oxide, a phenanthroline derivative, a benzonitrile derivative, a thermally activated delayed fluorescence material of a phosphorus oxide derivative as the second compound. The third compound preferably contains carbazole derivatives, triazine derivatives, pyrimidine derivatives, aniline derivatives, benzothiophene derivatives, benzofuran derivatives, fluorenyl derivatives.

Further, the connection layer comprises a first connection layer and a second connection layer, wherein the first connection layer and the second connection layer are respectively connected with two adjacent light-emitting layers, the first connection layer is of an alternating multilayer structure formed by m sub-electron transmission units and n ultrathin layers alternately, and the values of m and n are integers between 2 and 10.

Specifically, in one embodiment, the sub-electron transport unit is composed of a first organic material selected from at least one of the following compounds (1-1) to (1-21)

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In another embodiment, the sub-electron transport unit is comprised of an n-type dopant material and a second organic material. Wherein the n-type dopant material is selected from one of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, gold, silver, copper, iron, nickel, platinum, palladium, ruthenium, ytterbium, molybdenum trioxide, vanadium pentoxide, tungsten trioxide, cesium carbonate, lithium carbonate, sodium chloride, ferric chloride, and ferric oxide; the second organic material is selected from at least one of the compounds (5-1) to (5-42):

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further, the ultra-thin layer is formed of a material comprising an n-type dopant, wherein the n-type dopant material is preferably selected from at least one of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, gold, silver, copper, iron, nickel, platinum, palladium, ruthenium, ytterbium, molybdenum trioxide, vanadium pentoxide, tungsten trioxide, cesium fluoride, cesium carbonate, lithium fluoride, lithium carbonate, lithium 8-hydroxyquinolinate (Liq), sodium chloride, ferric chloride, and ferric oxide.

Further, the mass percentage of the n-type dopant material in the sub-electron transport unit is 0.1-50wt%; wherein the thickness of the ultrathin layer is 0.1-5nm, and the thickness of the electron transport unit is 3-30nm.

Further, the second connection layer comprises one or two of P-type dopant and aromatic amine compound, wherein the P-type dopant is MoO ₃ 、WO ₃ 、V ₂ O ₅ 、MoO ₂ 、Co ₃ O ₄ And at least one of the following compounds (HI-1) to (HI-20):

further, an electron transport layer of the organic electroluminescent device, which is an organic layer formed between a light emitting layer and a cathode layer (or an electron injection layer), mainly serves to transport electrons from a cathode to the light emitting layer. The electron transport layer may be composed of a layer of organic layer material, defined as a first electron transport layer; it is also possible to consist of two organic layers, the organic layer on the side close to the cathode layer being defined as a first electron transport layer and the organic layer on the side close to the light-emitting layer being defined as a second electron transport layer. The electron-transporting material used for the second electron-transporting layer is preferably an aromatic heterocyclic compound having 1 or more hetero atoms in the molecule, and particularly preferably a nitrogen-containing ring derivative. The nitrogen-containing ring derivative is preferably an aromatic ring having a nitrogen-containing six-membered ring or five-membered ring skeleton or a condensed aromatic ring having a nitrogen-containing six-membered ring or five-membered ring skeleton.

Further, the second electron transport layer of the organic electroluminescent device of the present invention is preferably selected from the following compounds but is not limited to the following structures:

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further, the film thickness of the electron transport layer is not particularly limited, and is preferably 10 to 100nm. Wherein when the electron transport layer of the organic electroluminescent device is composed of the first electron transport layer, the film thickness of the first electron transport layer is preferably 10-100 nm; when the electron transport layer of the organic electroluminescent device is composed of a first electron transport layer and a second electron transport layer, the film thickness of the first electron transport layer is preferably 9 to 70nm, and the film thickness of the second electron transport layer is preferably 1 to 30n m.

Further, the anode layer of the organic electroluminescent device mainly functions to inject holes into the hole transport layer or the light emitting layer, and anode layer materials having a work function of 4.5eV or more are preferably used. The anode layer material is preferably selected from Indium Tin Oxide (ITO), tin oxide (NESA), indium Gallium Zinc Oxide (IGZO), silver, and the like. The anode layer may be formed as an anode layer film by a thermal vapor deposition method, a sputtering method, or the like. The light transmittance of the visible region of the anode is preferably made greater than 80%. The sheet resistance of the anode layer is preferably 500 Ω/cm-1 or less, and the film thickness is preferably selected in the range of 10 to 200nm.

Further, the cathode layer of the organic electroluminescent device mainly functions to inject electrons into the electron injection layer, the electron transport layer or the light emitting layer, preferably a material having a small work function. The cathode material is not particularly limited, but is preferably selected from aluminum, magnesium, silver, magnesium-silver alloy, magnesium-aluminum alloy, aluminum-lithium alloy, and the like. The cathode layer may be formed as a cathode layer thin film by a thermal vapor deposition method, a sputtering method, or the like, and the cathode layer film thickness is preferably selected in the range of 10 to 200nm. Further, light emission may be extracted from the cathode side as needed.

Furthermore, the invention also provides a specific preparation method of the laminated organic electroluminescent device, and the preparation method of the platinum complex is further described by specific examples.

The source of the raw materials used in the following examples is not particularly limited and may be commercially available products or prepared by a preparation method well known to those skilled in the art.

Examples 1 to 5

(1) A glass substrate having an ITO transparent electrode (anode layer 10, film thickness of ITO: 95 nm) with a thickness of 30 mm. Times.30 mm. Times.0.7 mm was subjected to ultrasonic cleaning in acetone, a washing liquid, ultrapure water (3 times), and isopropanol in this order, and the ultrasonic cleaning time was 10 minutes for each step. Placing the cleaned ITO glass substrate in an oven at 80 ℃ for baking for 3 hours;

(2) Vacuum plasma cleaning treatment is carried out on the baked ITO glass substrate for 10 minutes;

(3) The glass substrate after plasma treatment is mounted on a substrate holder of a vacuum vapor deposition apparatus, and first, a compound HI-3 is deposited on a surface of a side on which transparent electrode lines are formed so as to cover the transparent electrodes, thereby forming a hole injection layer 101 having a film thickness of 10nm;

(4) Evaporating a compound HT-10 on the hole injection layer 101 to form a first hole transport layer 102 with a film thickness of 40 nm;

(5) Evaporating a compound HT-48 on the first hole transport layer 102 to form a second hole transport layer 103 with a film thickness of 10nm;

(6) Third compound RH and first compound RD were co-evaporated on second hole transport layer 103 to form first light-emitting layer 104 having a film thickness of 25nm, and the concentration of first compound RD in first light-emitting layer 104 was set to 4wt%, and the structures of third compound RH and first compound RD used were as follows:

(7) Evaporating EB-4 on the first light-emitting layer 104 to form a second electron transport layer 105 with the film thickness of 10nm;

(8) Evaporating ET-9 on the second electron transport layer 105 to form a first electron transport layer 106 with a film thickness of 30nm;

(9) Evaporating a first connecting layer 107 on the first electron transport layer 106, wherein the film thickness is 20nm;

(11) Evaporating a second connection layer 108 co-evaporated from HI-7 and HT-10 on the first connection layer 107, wherein the doping concentration of HI-7 is set to 3wt% and the film thickness is 10nm;

(12) Evaporating a compound HT-10 on the second connection layer 108 to form a third hole transport layer 109 with a film thickness of 30nm;

(13) Evaporating a compound HT-48 on the first hole transport layer 109 to form a fourth hole transport layer 110 with a film thickness of 10nm;

(14) Co-evaporating a third compound RH and a first compound RD on the second hole transport layer 110 to form a second light emitting layer 111 having a film thickness of 25nm, wherein the concentration of the first compound RD in the second light emitting layer 111 is set to 4wt%;

(15) Evaporating EB-4 on the second light-emitting layer 111 to form a fourth electron transport layer 112 with a film thickness of 10nm;

(16) Evaporating ET-9 on the second electron transport layer 112 to form a third electron transport layer 113 with a film thickness of 30nm;

(17) Evaporating Liq on the first electron transport layer 113 to form an electron injection layer 114 with a film thickness of 2 nm;

(18) Metal Al was deposited on the electron injection layer 114 to form a cathode layer 115 having a film thickness of 100nm.

The compound combinations and the graded doping processes used for the first connection layer 107 formed in step (9) are shown in examples 1 to 5 of table 1 below.

TABLE 1

Comparative examples 1 and 2

In the laminated organic electroluminescent devices prepared in comparative examples 1 and 2, a first connection layer 107 having a film thickness of 20nm was deposited between a first electron transport layer 106 and a second connection layer 108, and the compounds used for the first connection layer 107 were as described in Table 2 below. Except for this, a stacked organic electroluminescent device was produced in the same manner as in examples 1 to 5.

TABLE 2

Comparative example	1	2
			Compounds of formula (I)	5 mass% lithium carbonate: 1-2	5 mass% cesium carbonate: 1-12
Thickness (nm)	20	20

Evaluation of organic electroluminescent device Performance

The organic electroluminescent devices prepared in examples 1 to 5 and comparative examples 1 to 2 were measured using a spectroradiometer CS-2000 (Konica Minolta) and a digital source meter 2420 (Keithley) and the driving voltage, external Quantum Efficiency (EQE) and CIE1931 chromaticity coordinates (x, y) when the prepared organic electroluminescent devices were driven at a current density of 10mA/cm 2; using a device lifetime test to measure a lifetime (T95) in which the luminance of the device decays to 95% of an initial luminance and a difference (Δv) between a driving voltage and the driving voltage at the initial luminance when the prepared organic electroluminescent device is driven at a current density of 50mA/cm 2; the results of evaluating the device properties of examples 1 to 5 and comparative examples 1 to 2 are shown in Table 3 below.

TABLE 3 Table 3

Comparing the device driving voltages of examples 1 to 5 and comparative examples 1 to 2 in table 1, the first connection layer adopts an alternating stacked structure formed by the ultrathin layer and the electron transfer units, the device driving voltage is lower than that of the comparative example, which indicates that the introduction of the alternating structure is beneficial to improving the carrier generating capacity of the connection layer and reducing the voltage drop at the connection layer; in the comparison of example 1 with comparative example 1 and example 2 with comparative example 2, respectively, after the electron transport structure composed of the ultrathin layer and the electron transport unit alternately is introduced into the first electron transport layer, the T95 lifetime of the device is improved, and the rise of the driving voltage in the aging process of the device is reduced, which means that the first connection layer of the alternating combination structure can inhibit the alkali metal from entering the light emitting layer, so that the brightness attenuation of the device is slowed down, and the ultrathin layer can inhibit the aging of the electron transport material in the first connection layer, so that the rising trend of the driving voltage of the device is retarded. In the case where the electron transport units of the examples use different electron transport materials and the ultrathin n-type dopant materials, the device lifetime and the difference Δv are better than those of the comparative examples, and the beneficial effects of the first connection layer structure formed by alternately forming the ultrathin layer and the electron transport units of the comparative examples 1 to 5 and the comparative examples 1 to 2, such as the reduction of the driving voltage of the stacked device, the improvement of the device lifetime and the reduction of the driving voltage trend in the aging process of the device, are more general effects.

Although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The laminated organic electroluminescent device is characterized by comprising an anode layer, at least two light-emitting units, a cathode layer and a connecting layer, wherein the anode layer, the at least two light-emitting units and the cathode layer are sequentially arranged from bottom to top; the connecting layer comprises a first connecting layer and a second connecting layer, the first connecting layer and the second connecting layer are respectively connected with the two adjacent light-emitting units, and the first connecting layer is formed into an alternate lamination structure by m sub-electron transmission units and n ultrathin layers.

2. A stacked organic electroluminescent device as claimed in claim 1, wherein said ultra-thin layer comprises an n-type dopant material, preferably at least one from the group consisting of lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, gold, silver, copper, iron, nickel, platinum, palladium, ruthenium, ytterbium, molybdenum trioxide, vanadium pentoxide, tungsten trioxide, cesium fluoride, cesium carbonate, lithium fluoride, lithium carbonate, lithium 8-hydroxyquinolinate, sodium chloride, ferric chloride and ferric oxide.

3. The laminated organic electroluminescent device of claim 1, wherein m and n are integers between 2 and 10.

4. The laminated organic electroluminescent device according to claim 1, wherein the sub-electron transport unit is composed of a first organic material having electron transport properties, the first organic material being selected from at least one of the following compounds (1-1) to (1-21):

5. the laminated organic electroluminescent device of claim 1, wherein the sub-electron transport unit is composed of an n-type dopant material and a second organic material;

6. the laminated organic electroluminescent device of claim 1, wherein the second connection layer comprises one or both of a P-type dopant and an aromatic amine compound.

7. The laminated organic electroluminescent device of claim 6, wherein the P-type dopant is at least one of MoO3, WO3, V2O5, moO2, co3O4, and the following compound (HI-1) -compound (HI-20):

8. the organic electroluminescent device of claim 5, wherein the mass percentage of the n-type dopant material of the sub-electron transport unit is 0.1-50 wt%.

9. The organic electroluminescent device of claim 1, wherein the ultra-thin layer has a thickness of 0.1 to 5nm and the sub-electron transport unit has a thickness of 3 to 30nm.

10. An apparatus for laminating organic electroluminescent devices, characterized in that the apparatus comprises the organic electroluminescent device according to any one of claims 1 to 9, and is not limited to the organic electroluminescent device, and includes a display device, an illumination device, a solar cell, an illumination element, an organic thin film transistor, an organic field effect transistor, an organic thin film solar cell, an information tag, or electronic paper made using the device structure and material according to any one of claims 1 to 9.